1. Field of the Invention
The present invention relates to an image processing system for processing image information as electric signals.
2. Description of the Prior Art
A photocopying machine for duplicating images of an original is widely used as a processing system of image information. The system of this type adopts a general electrophotography device wherein an original is exposed to light emitted by a light source, such as a fluorescent light, the light reflected by the original is guided to a photosensitive body to form an electrostatic latent image thereon, and the electrostatic latent image is visualized according to a known developing means. However, when duplicating only part of an original with a conventional device, undesired portions of the original are masked or cut away for duplication of the desired portion, resulting in inconvenience.
Another type of image processing system has also been proposed wherein the image of an original is read out to generate corresponding electric signals which are processed electrically. With this type of system, in addition to the functions of the system of the former type, other kinds of image processing may be performed such as duplication of part of an original, synthesis of a plurality of images, or variation of the density of the image at only part of the original.
For example, it has been proposed to convert the image information of an original into electric signals by a solid image sensor such as a CCD and to electrically process the obtained electric signals, so that part of the original may be separated from the rest of the original. For this purpose, it is possible to limit the area for readout of the solid image sensor or to store the readout image information in a memory and to read out only the required information from the memory. When a memory is used, once the image information of the original is stored in the memory, the image information may be used for separation of desired parts, and the efficiency in office work may thus be improved. However, input of the address for outputting the image information stored in the memory is performed by supplying from a keyboard numerical data representing the addresses or by specifying the desired portion of the original displayed on a CRT using a light pen. Numeral setting for input from the keyboard requires a large quantity of address data.
In addition to this, the system of this kind becomes complex in structure, and the operation becomes difficult with an increase in the number of functions incorporated therein. This type of system may thus be operated only by those who are well acquainted with the operating procedure, and the image processing time may become very long, also resulting in inconvenience.
With a system in which image information is stored once in a memory means and the desired image information is accessed, various kinds of image processings may be performed. However, since the procedure involves storing of the image information in a memory means, the readout time of the image information from the memory means affects the processing time, and counters must also be incorporated for specifying the addresses in the memory means. DMA transfer is utilized for the transfer of the image information. When DMA transfer is utilized, high-speed reading of the image information into and out of the memory means may be achieved. However, since the addresses in the memory means are generally consecutive for each scanning operation, the initial address and the final address corresponding to the desired portion of the original must be specified corresponding to the number of subscanning operations of the image information. This number of specifying operations of addresses increases as the image element density is made higher.